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https://issues.apache.org/jira/browse/CALCITE-3878?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17073241#comment-17073241
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Julian Hyde commented on CALCITE-3878:
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bq. So the debate make me think what shall we do in the future as a principle?
Allow new ArrayList with capacity or not?
I don't think we new principles. We should trust code authors to do the right
thing for a particular piece of code. The code is, as far as we know, just fine
already.
If a list typically has 2 or 3 elements, probably don't use size. If a list may
have hundreds of elements, and is performance-critical. specify a size.
How about you revise your PR and remove sizes where they don't make much
difference? Then I'd be OK accepting it.
> Make ArrayList creation with initial capacity when size is fixed
> ----------------------------------------------------------------
>
> Key: CALCITE-3878
> URL: https://issues.apache.org/jira/browse/CALCITE-3878
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Affects Versions: 1.22.0
> Reporter: neoremind
> Priority: Minor
> Labels: pull-request-available
> Time Spent: 1h 10m
> Remaining Estimate: 0h
>
> I find many places in Calcite where _new ArrayList<>()_ is used, if the list
> is expected to be immutable or not resizing, it is always a good manner to
> create with initial capacity, better for memory usage and performance.
> I search all occurrences, focus on the core module, to make it safe, I only
> update local variables with fixed size and not working in recursive method.
> If the local variable reference goes out of scope, if resizing is needed,
> things will work normally as well, so no side effect, but for the "escaping"
> case, I am very conservative and do not change them.
>
>
>
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